As a general model for studying the regulation of immune responses, the expression of light chains encoded by the lambda gene family will be analyzed at various levels. The analysis will seek initially to explain the great diversity in the frequency of diverse lambda chain subtypes in antibodies of different specificity. The frequency of lambda chains will be measured in the anti-DNP and anti-NP antibodies elicited in the mice subjected to simultaneous immunizations with DNP an NP antigens; the rates of synthesis of the various lambda chain subtypes also will be measured, as will the frequency of the B cells that produce each of the subtypes. Regulatory mechanisms also will be evaluated at the level of (1) V lambda gene segment rearrangements, (2) the rate of translation of mRNA, and (3)\the influence of recombining various lambda chains with individual heavy chains will be assessed in terms of the affinities of the resulting recombinant antibody molecules. Affinity maturation of antibodies having different lambda chain subtypes also will be determined, and selected lambda chains, derived from early, low affinity antibody molecules, and other lambda chains, derived from late, high affinity molecules, will be sequenced in their V regions. The "primer extension" method for sequencing lambda chain cDNA will be developed to increase the speed and decrease the cost of determining V region sequences of lambda chains. The sequenced chains also will be used in collaborative studies to determine whether they can elicit immune responses that result in specific resistance to the myeloma cells that produce these chains.